Pyrrhotite nano-inclusions in apatite from Les Guilleries lamprohyres (NE Iberian Peninsula)

Apatite is ubiquitous in most types of rocks but in trace amounts, and can form by a variety of processes. Apatite is of great interest because it is an important carrier of volatiles (F, Cl, and OH) and rare-earth elements (REEs), and can be used to reconstruct petrogenetic processes in different environments (e.g., [1]). However, very few studies are dedicated to understanding apatite microstructures (e.g., [2]). Here, we explore apatite in Les Guilleries lamprophyre dykes to gain insights into the parental melt and potential processes of re-mobilization of REEs. The studied dykes are calc-alkaline and represent upwelling of deep lithospheric mantle material (least modified magmas) that emplaced at the end of the Hercynian orogeny in a variety of igneous rocks [3]. The texture and composition of apatites were examined in two thin sections of the least altered dykes, numbered GUI-40 and GUI-41, using SEM/EDS, EPMA, and FIB-TEM. Our results show that apatites in GUI-40 are REE-depleted, mostly rounded, subhedral, and range from ~5 to ~35 μm in size. Their average X-site occupancy is F=78, Cl=2, and OH=20 (mol%). Apatites in GUI-41 are highly acicular (~3-10 μm wide and up to ~120 μm long), REE-enriched compared to GUI-40, and their average X-site occupancy is F=64, Cl=5, and OH=31 (mol%). TEM work on an apatite grain in GUI-40 reveals the presence of abundant nano-inclusions, ~10-60 nm in size, with euhedral, hexagonal shapes in the apatite core (Fig. 1). The nano-inclusions are (i) fully occupied by pyrrhotite, (ii) half occupied by pyrrhotite, or (iii) completely empty. The data suggest that apatites in GUI-40 are primary and their microstructure reflect immiscibility of liquids, interpreted as a characteristic inherited from the primary lamprophyre melt. The presence of Fe in the magma and/or the reducing conditions likely prevented S to form ellestadite domains within the apatite structure. This study also demonstrates that slight REE re-mobilization did occur during a secondary, hydrothermal event

Single amino acid mutation controls hole transfer dynamics in DNAmethyltransferase HhaI complexes

Different mutagenic effects are generated by DNA oxidation that implies the formation of radical cation states (socalled holes) on purine nucleobases in the π stack. The interaction of DNA with proteins may protect DNA from the oxidative damage owing to hole transfer (HT) from the stack to aromatic amino acid residues. The HT dynamics is such systems is still poorly understood. Here, we report a computational study of HT in DNA complexes with methyltransferase HhaI and its mutant Q237W, which were experimentally investigated in the Barton group. We employ a combined approach based on molecular dynamics simulations and quantum mechanical calculations to estimate the rate for all individual steps involved in the HT pathways; finally the overall HT kinetics are explored using the Monte-Carlo method. Our results indicate that the HT characteristics are strongly affected by structural deformations of DNA upon its binding to the protein. In the wild-type enzyme complex, a Gln residue inserted in the DNA π-stack is shown to destabilize the radical cation states of neighboring guanines and thereby inhibits the long-range HT in line with experimental findings. In contrast, the HT is estimated to be quite fast in a complex of the Q237W mutant where Trp237 stabilizes hole states on the adjacent G bases and enhances the electronic coupling of these sites. An alternative HT pathway that implies the formation of a Trp+ radical is predicted to be less efficient. Our study provides a consistent molecular picture on how long-range HT in DNA-protein complexes is controlled by amino acids closely interacting with the π stack.Peer Reviewe

Single amino acid mutation controls hole transfer dynamics in DNAmethyltransferase HhaI complexes

Different mutagenic effects are generated by DNA oxidation that implies the formation of radical cation states (socalled holes) on purine nucleobases in the π stack. The interaction of DNA with proteins may protect DNA from the oxidative damage owing to hole transfer (HT) from the stack to aromatic amino acid residues. The HT dynamics is such systems is still poorly understood. Here, we report a computational study of HT in DNA complexes with methyltransferase HhaI and its mutant Q237W, which were experimentally investigated in the Barton group. We employ a combined approach based on molecular dynamics simulations and quantum mechanical calculations to estimate the rate for all individual steps involved in the HT pathways; finally the overall HT kinetics are explored using the Monte-Carlo method. Our results indicate that the HT characteristics are strongly affected by structural deformations of DNA upon its binding to the protein. In the wild-type enzyme complex, a Gln residue inserted in the DNA π-stack is shown to destabilize the radical cation states of neighboring guanines and thereby inhibits the long-range HT in line with experimental findings. In contrast, the HT is estimated to be quite fast in a complex of the Q237W mutant where Trp237 stabilizes hole states on the adjacent G bases and enhances the electronic coupling of these sites. An alternative HT pathway that implies the formation of a Trp+ radical is predicted to be less efficient. Our study provides a consistent molecular picture on how long-range HT in DNA-protein complexes is controlled by amino acids closely interacting with the π stack.Peer Reviewe

Single Amino Acid Mutation Controls Hole Transfer Dynamics in DNA-Methyltransferase HhaI Complexes

Different mutagenic effects are generated by DNA oxidation that implies the formation of radical cation states (so-called holes) on purine nucleobases. The interaction of DNA with proteins may protect DNA from oxidative damage owing to hole transfer (HT) from the stack to aromatic amino acids. However, how protein binding affects HT dynamics in DNA is still poorly understood. Here, we report a computational study of HT in DNA complexes with methyltransferase HhaI with the aim of elucidating the molecular factors that explain why long-range DNA HT is inhibited when the glutamine residue inserted in the double helix is mutated into a tryptophan. We combine molecular dynamics, quantum chemistry, and kinetic Monte Carlo simulations and find that protein binding stabilizes the energies of the guanine radical cation states and significantly impacts the corresponding electronic couplings, thus determining the observed behavior, whereas the formation of a tryptophan radical leads to less efficient HT

El proceso de intercambio comercial sudamericano y las crisis económicas

Economic crises can be both obstacles and opportunities for strengthening the South American trade integration process. The hypothesis is that when crises are intra-regional trade is directed out of the region, weakening the trade integration process; on the contrary, when crises have extra regional origin intraregional trade increases, intensifying this process. The aim is to study the evolution of the South American trade flows during the period 1990-2010 in accordance with any changes that occurred after the economic crisis.  Trade flows of industrial manufactures are analyzed from three perspectives: composition, size, origin and destination. The methodology is based on the construction of economic index an on descriptive statistical analysis. It is concluded that, in general terms, studies of magnitude and origin and destination are consistent with the hypothesis of the work but not the analysis of the composition.Las crisis económicas pueden constituir tanto obstáculos como oportunidades de fortalecimiento del proceso de integración comercial sudamericano. La hipótesis propuesta sugiere que cuando las crisis son intrarregionales el comercio se orienta hacia afuera de la región debilitando el proceso de integración comercial; por el contrario cuando las crisis tienen origen extra regional el comercio intrarregional aumenta, intensificando tal proceso. El objetivo es estudiar la evolución del flujo comercial sudamericano durante el período 1990-2010 atendiendo a posibles cambios acontecidos luego de las crisis económicas. Para ello se analiza el comportamiento de los flujos de comercio de las manufacturas industriales desde tres perspectivas: composición, magnitud y origen y destino. La metodología empleada se basa en la construcción y aplicación de diversos índices económicos y análisis estadístico descriptivo, utilizando datos del Banco Mundial (WITTS) y CEPAL. Se concluye que, en términos generales, los estudios sobre magnitud, y origen y destino se condicen con la hipótesis del trabajo pero no así el análisis sobre la composición

How abasic sites impact hole transfer dynamics in GC-rich DNA sequences

Changes in DNA charge transfer properties upon the creation of apurinic and apyrimidinic sites have been used to monitor DNA repair processes, given that such lesions generally reduce charge transfer yields. However, because these lesions translate into distinct intra and extrahelical conformations depending on the nature of the unpaired base and its DNA context, it is unclear the actual impact of such diverse conformations on charge transfer. Here we combine classical molecular dynamics, quantum/molecular mechanics (QM/MM) calculations, and kinetic Monte Carlo simulations to investigate the impact of abasic sites on the structure and hole transfer (HT) properties of DNA. We consider both apurinic and apyrimidinic sites in polyG and polyGC sequences and find that most situations lead to intrahelical conformations where HT rates are significantly slowed down due to the energetic disorder induced by the abasic void. In contrast, the presence of an unpaired C flanked by C bases leads to an extrahelical conformation where stacking among G sites is reduced, leading to an attenuation of electronic couplings and a destabilization of hole states. Interestingly, this leads to an asymmetric HT behavior, given that the 5′ to 3′ transfer along the G strand is slowed down by one order of magnitude while the opposite 3′ to 5′ transfer remains similar to that estimated for the reference polyG sequence. Our simulations thus suggest that electrochemical monitoring of the DNA repair process following changes in charge transfer properties can miss repair events linked to abasic sites adopting extrahelical conformations

Electronic energy transfer in biomacromolecules

Electronic energy transfer is widely used as a molecular ruler to interrogate the structure of biomacromolecules, and performs a key task in photosynthesis by transferring collected energy through specialized pigment-protein complexes. Förster theory, introduced over 70 years ago, allows linking transfer rates to simple structural and spectroscopic properties of the energy‐transferring molecules. In biosystems, however, significant deviations from Förster behavior often arise due to breakdown of the ideal dipole approximation, dielectric screening effects due to the biological environment, or departure from the weak‐coupling regime. In this review, we provide a concise overview of advances in simulations of energy transfer in biomacromolecules that allow overcoming the main limitations of Förster theory. We first discuss advances in quantum chemical methods to compute electronic couplings, their extension to multiscale formulations to include screening effects, and strategies to treat the interplay between coupling fluctuations and energy transfer dynamics. We then examine the spectral overlap term, and how this quantity can be estimated from simulations of the spectral density of exciton-phonon coupling. Finally, we discuss rate theories that can describe energy transfers in situations where strong coupling leads to delocalized excitions, a common situation found in closely packed multichromophoric systems such as photosynthetic complexes and nucleic acids

The south american commercial exchange process and the economic crises

Las crisis económicas pueden constituir tanto obstáculos como oportunidades de fortalecimiento del proceso de integración comercial sudamericano. La hipótesis propuesta sugiere que cuando las crisis son intrarregionales el comercio se orienta hacia afuera de la región debilitando el proceso de integración comercial; por el contrario cuando las crisis tienen origen extra regional el comercio intrarregional aumenta, intensificando tal proceso. El objetivo es estudiar la evolución del flujo comercial sudamericano durante el período 1990-2010 atendiendo a posibles cambios acontecidos luego de las crisis económicas. Para ello se analiza el comportamiento de los flujos de comercio de las manufacturas industriales desde tres perspectivas: composición, magnitud y origen y destino. La metodología empleada se basa en la construcción y aplicación de diversos índices económicos y análisis estadístico descriptivo, utilizando datos del Banco Mundial (WITTS) y CEPAL. Se concluye que, en términos generales, los estudios sobre magnitud, y origen y destino se condicen con la hipótesis del trabajo pero no así el análisis sobre la composición.Economic crises can be both obstacles and opportunities for strengthening the South American trade integration process. The hypothesis is that when crises are intra-regional trade is directed out of the region, weakening the trade integration process; on the contrary, when crises have extra regional origin intraregional trade increases, intensifying this process. The aim is to study the evolution of the South American trade flows during the period 1990- 2010 in accordance with any changes that occurred after the economic crisis. Trade flows of industrial manufactures are analyzed from three perspectives: composition, size, origin and destination. The methodology is based on the construction of economic index an on descriptive statistical analysis. It is concluded that, in general terms, studies of magnitude and origin and destination are consistent with the hypothesis of the work but not the analysis of the composition.Fil: Tortul, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Económicas y Sociales del Sur. Universidad Nacional del Sur. Departamento de Economía. Instituto de Investigaciones Económicas y Sociales del Sur; ArgentinaFil: Corbella, Virginia Inés. Universidad Nacional del Sur. Departamento de Economía; Argentin

Spectral variability in phycocyanin cryptophyte antenna complexes is controlled by changes in the α‐polypeptide chains

Quantitative models of light harvesting in photosynthetic antenna complexes depend sensitively on the challenging determination of the relative site energies of the pigments. Here we analyze the basis of the light harvesting properties of four antennae from cryptophyte algae, phycocyanines PC577, PC612, PC630 and PC645, by comparing two alternative theoretical strategies to derive the excitonic Hamiltonian. The first is based on molecular dynamics simulations and subsequent polarizable quantum/molecular mechanics (QM/MMPol) calculations, whereas the second is based on three-layer QM/MMPol/ddCOSMO calculations performed on optimized geometries of the pigments, where the water solvent is described using the ddCOSMO continuum model. We find the latter approach to be remarkably accurate, suggesting that these four phycobiliproteins share a common energetic ordering PCB82 < PCB158 < DBV51/61 for pigments located in the highly-conserved β chains, whereas bilins in the more divergent α chains originate their spectral differences. In addition, we predict a strong screening of the coupling among central DBVs in 'open' form complexes PC577 and PC612 compared to 'closed' form ones, which together with the increased interpigment separation explains the attenuation of coherence beatings observed for these complexes

Motivation for Therapy: an important ingredient to change?

We analyse the levels of motivation for therapy, as well as explore if there are significant differences between the group of clients who drop-out from therapy and those who continue. Is there a relation between the different dimensions of motivation and the way the client perceive the therapeutic environment? 39 dyads of therapist and clients from Portugal participated. The Client motivation for therapy scale, adapted from Pelletier, Tucson and Haddad (1997) and the modified HCCQ from Williams, McGregor, King, Nelson and Glasgow (2005) were administered to the clients in 1st, 3rd, 5th and 8th session. Significant differences in the intrinsic motivation and amotivation dimension and no significant differences were found, between those who give up/continue psychotherapy (p>.05). Nevertheless it was found a positive significant correlation (rs=.467) between the level of perception of the therapeutic environment and integrated motivation, as well as a negative correlation with amotivation (rs=.521), that is to say, the better the perception of the therapeutic environment, more motivated they are for therapy.Keywords: motivation, psychotherapy, clients, therapeutic environment